In the US, the two main organizations who set electrical safety standards for electrical enclosures are NEMA (National Electrical Manufacturers Association) and UL (Underwriters Laboratories). Although the standards for each enclosure type are independent from each other, the protection expectations are mostly the same. UL ratings are often described in more technical language, but after reviewing the summarized protections in the "NEMA and UL Ratings Equivalency Chart" below, you’ll quickly see that the enclosure protection expectations are almost identical.
So what’s the main difference between NEMA and UL ratings?
Besides the specific language used to define each enclosure rating, the main difference lies in the testing requirements.
UL Testing Requirements:
To receive a UL certification mark, the manufacturer must send samples of the enclosure to a third-party qualified evaluator to determine if it’s compliant. Afterwards, the third-party evaluator will continue to do periodic audits of the manufacturing specifications and the enclosure materials.
NEMA Testing Requirements:
NEMA does not require third-party testing to verify the NEMA rating. The manufacturer alone can determine if the enclosure is in compliance. For example, one company that we supply enclosures to has their own testing area to verify the NEMA rating on their enclosures. If the enclosures pass the NEMA testing, the company can then send them off for UL testing as needed.
NEMA and UL Ratings Equivalency Chart
Click here, or on the chart to view it as a PDF:
You might also want to check out our NEMA Enclosure Types and IP Equivalency Chart to see how NEMA ratings compare to IP ratings.
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